56 Telephone Systems of the Continent of Europe 



SWITCHING ARRANGEMENTS 



Hitherto ' standard ' boards of the Western Electric Company 

 have been used at the principal switch-rooms, so it may be 

 imagined that smart management has been requisite at Munich, 

 with its 5,000, and Nuremberg, with its 2,500 subscribers, in order 

 to provide an acceptable service. But multiple switch-boards 

 have been ordered for, and will soon be fitted at, both these 

 centres. They are of the same company's manufacture, with self- 

 restoring drops of the type already installed at Zurich, and which 

 is described in the Swiss section (p. 390). Fig. 8 is a plan of a 

 recent Bavarian switch-board for small centres, showing how both 

 single and double subscribers' lines and trunk wires are dealt with. 

 The bar commutator is for cross-connecting and joining any wire 

 temporarily to the testing apparatus. This bar commutator is 

 sometimes replaced in the larger exchanges by a cross-wire 

 commutator invented by Mr. J. Baumann, an engineer of the 

 Royal Bavarian Telephone Department, which, for a large number 

 of lines, is far cheaper to construct, while it occupies less space 

 and is simpler to manipulate. Mr. Baumann's cross-connecting 

 board consists of a strong rectangular iron frame encased in 

 beechwood, and arranged to receive a number of silicium bronze 

 wires of 8 mm. diameter, strung, some horizontally and some 

 vertically, so as to cross each other at right angles at a distance of 

 some two centimeters. The wires are insulated at the frames, 

 and provided with tightening screws, similar to those of a violin 

 (a tension of from thirteen to sixteen kilogrammes is kept normally 

 on the wires), and connection terminals, by which the horizontal 

 wires are joined to the subscribers' lines and the vertical wires to 

 the switch-board. Under the tension applied, the wires remain 

 so taut that it is not found necessary in practice to allow a greater 

 clearance between parallel conductors than from three to five 

 millimeters. The necessary connections between the horizontal 

 and vertical wires are effected by small brass plates, each bearing 

 two hooks about one centimeter apart, one hook adjusted to hold 

 a horizontal, the other a vertical, wire. When two such wires, 



